1. Field of the Invention
This invention relates to a multicolor offset perfecting press adapted to multicolor print paper sheets successively transported from a feeder station on both sides thereof.
2. Description of the Related Art
Most of the conventional multicolor offset perfecting presses are adapted to four-color print the top side and to four-color print the back side of the paper sheet. It is known to assemble compression cylinders integrally so that they are successively in contact and operatively associated one with another in a longitudinally zigzag configuration (Japanese Patent Publication No. 1991-21346). A perfecting press of the above-mentioned type is well-known, in which the compression cylinders are horizontally in contact and operatively associated with one another and integrally assembled together with the offset cylinders and the plate cylinders so that the back side of the paper sheet cannot be printed more than two colors (Japanese Patent Application Disclosure Gazette No. 1988-87234). A multicolor offset perfecting press is also well-known which comprises top side printing units each having a single offset cylinder in contact and operatively associated with an upper portion of each compression cylinder included in the top side printing units, and back side printing units each having a single offset cylinder in contact and operatively associated with a lower portion of each compression cylinder included in the back side printing units so that the top side printing units and back side printing units are alternately in contact and operatively associated together (Japanese Patent Application Disclosure Gazette No. 1994-336003).
The press disclosed in Japanese Patent Publication No. 1991-21346 cannot be used in practice since, if it is desired to multicolor print a paper sheet of a relatively large size, the total height of the press will be unacceptably large. The press proposed by Japanese Patent Application Disclosure Gazette No. 1988-87234 also cannot be used in practice, since this press includes a delivery cylinder having a diameter that is too large to keep offset cylinders in contact with a compression cylinder which is in contact and operatively associated with the delivery cylinder. In addition, this press cannot print the back side of the paper sheet more than two colors. Finally, the press disclosed in Japanese Patent Application Disclosure Gazette No. 1994-336003 comprises the top side printing units and the back side printing units alternately in contact and operatively associated with the top side printing units, and a single-color printing is achieved by each printing unit. To achieve four-color printing on the top side and four-color printing on the back side, this press requires eight compression cylinders. This means that the number of times the paper sheet is transferred from one cylinder to the next cylinder and, in consequence, a desired print registering and, therefore, high precision multicolor printing cannot be expected.